1. Technical Field of the Invention
The present invention relates to sterile instruments for use with microscopes for operations in microsurgical, such as neurosurgical and orthapedic, operations.
2. Related Art
The recent advances in operating methods and instruments have made microsurgery a routine practice. In microsurgery, a microscope for operations is employed to examine, at an increased magnification, the part of a patient being operated on. A common method of sterilizing the microscope for operation is to cover it with an already sterilized drape so that its exterior portions are rendered in an aseptic condition.
To keep the surgeon in a sterile condition, a sterile cap may be mounted on those parts of a microscope for operation which an operator may manipulate during the surgical operation, and U.S. Pat. No. 5,036,446 proposed the use of a sterile cap for handling surgical lamps.
Turning back to the drape, it is dimensioned to be larger than the microscope for operation so that it can smoothly mount over the latter but that it will not degrade the manipulability of the enclosed microscope. After covering the microscope for operation, loose portions of the drape are usually gathered by rubber bands or tie strings and secured to support arms and the like of the microscope.
However, during actual use, the drape must have a certain allowance for permitting free movements of the moving parts of the microscope for operation but in the fixing method just described above, the degree of loosening of the drape has to be adjusted with the microscope being actually manipulated and this has been one of the reasons that a prolonged time is required in making preparations for a surgical operation. Furthermore, loose portions of the drape can interfere with the vision of the surgeon or they may accidentally contact nonsterilized parts. In addition, the drape is discarded after use but this only adds to the running cost of surgical operations.
The sterile cap described in U.S. Pat. No. 5,036,446 also is not problem-free. Those parts of the microscope for operation which are not covered with the cap are non-sterile and may accidentally be touched by the surgeon during the surgical operation. In addition, if more than one part of the microscope is to be manipulated, the sterile cap must be mounted on each of such parts and this again increases the time required in making preparations for a surgical operation. This, both the drape and the sterile cap have encountered considerable difficulty in use.
The sterilization of a microscope for operations is held to be particularly necessary in neurosurgical and orthapedical operations in order to protect the patient, surgeon and other operating staff-members against injections. To meet this requirement, the microscope for operation body and its support arm portions are commonly enclosed with covers made from sterile fabrics or synthetic resins in a bag shape. However, if the sterile cover has loose portions, it may prevent smooth movements of the support arm portions or the loose portions may accidentally contact non-sterile parts, thereby interfering with the surgical operation. To avoid these problems, binding the sterile cover to the support arm portions and the like by fastening means such as tie strings or rubber bands is commonly practiced. However, depending on the binding position or strength, the movable range of the support arm portions may be narrowed, thereby making it impossible for the microscope for operation to be manipulated to the fullest extent. As a further problem, the loosening of the portions of the cover other than those which are bound with strings or rubber bands is not completely eliminated and the portions that remain loose can potentially obstruct the vision of the surgeon. Thus, the manipulability of the microscope for operation has been more or less dependent on the skill of the operating staff-member who binds the cover to the support arm portions and the like by strings or rubber bands.
Another example of the sterile drape is disclosed in U.S. Pat. No. 3,698,791. This is a deformable drape generally adapted to the shape of the microscope for operation such that it can completely cover the latter in one action. A different approach is disclosed in U.S. Pat. No. 5,355,292 and covers that can be sterilized by autoclaving or the like are placed over the respective handles of the microscope for operation to be used and the surgeon will manipulate only the covered handles so as to keep them in a sterile condition throughout the surgical operation.
The drape shown in U.S. Pat. No. 3,698,791 is convenient in that it can cover the whole part of the microscope for operation in one action but on the other hand any unwanted loose portions of the drape have to be secured to selected parts of the microscope because they will reduce the efficiency of surgical operations by interfering with the smooth movements of the surgeon's hands or obstructing his or her vision during observation with the naked eye. However, if the number of sites where loose portions are secured or the amount in which they are secured is increased, smooth movements of the arms for moving the microscope for operation body and other parts that make relative movements to one another may be prevented, thereby rendering it impossible for the microscope to exhibit its intended performance. Needless to say, securing the loose portions of the drape to selected parts of the microscope for operation while check is made to insure that those parts which are to make relative movements move smoothly is a very tedious job. What is more, in order to manipulate the covered parts of the microscope for operation as in making pupil distance adjustments or manual zooming, the parts under manipulation have to be grasped through the drape but slippage often occurs between the microscope and the drape, thereby reducing its manipulability. Another problem with the drape disclosed in U.S. Pat. No. 3,698,791 is that being of a bag shape, it must have a sufficient bore to admit the largest-diameter portion of the microscope for operation and this results in the formation of too many loose portions.
In order to eliminate the loose portions of the bag-shaped drape after it has been mounted over the microscope for operation, U.S. Pat. No. 3,698,791 proposes the use of bands. However, as already mentioned, eliminating the loose portions of the drape in a satisfactory manner for practical purposes is difficult and, what is more, when those parts of the microscope for operation which are adapted to move relative to one another move during the surgical operation, the applied bands may be displaced in such a way as to increase the sag of loose portions. According to U.S. Pat. Nos. 4,045,118 and 4,561,540, tear lines are formed in selected areas of the drape and the unwanted portions of the drape will be severed off along those tear lines after it has been placed over the microscope for operation. A problem with this proposal is that if an excessive force is inadvertently applied to the microscope when the unwanted portions of the drape are cut off, the diopter of the eyepieces might deviate from preset values or they could fail to function properly.
A clinical practice that is gaining popularity today in the field is using an endoscope in order to examine "blind areas" which are inaccessible to a microscope for operation as disclosed in Unexamined Published Japanese Patent Application No. Hei. 6-000196. An endoscope is to be inserted into a body cavity, so it is sterilized separately and independently from the microscope for operation. Hence, according to the patent reference, supra, the drape for a one-piece assembly of an microscope for operation and endoscope combination has a hole through which the tip of the objective lens of the endoscope is to be exposed. However, if the drape is placed over the one-piece combination of a microscope for operation and an endoscope, the endoscope which has been sterilized independently of the drape may be contaminated by the inside surface of the bag-shaped drape which may have been contacted by non-sterile portions of the equipment. As a further problem, the hole through which the tip of the objective lens of the endoscope is to be exposed may also allow the microscope for operation to become exposed, thereby impairing the integrity of sterilization.
Further, as taught in U.S. Pat. No. 3,698,791, the drape is usually delivered in a folded condition to hospitals, where it is unfolded into a bag shape so that it can be placed over the microscope for operation. In order to insure that the inner surface of the bag which will contact the microscope for operation when it is covered by the drape will not be touched by non-sterile personnel, the drape as it is delivered to hospitals is folded in such a way that said inner surface will come outside. In fact, however, the drape is typically made of transparent vinyl polymers, so when it is in a folded condition, it is hard to tell which side is the interior and which is the exterior and this can potentially lead to the contamination of these areas which should be kept in a sterile condition.
The cover described in U.S. Pat. No. 5,355,292 is provided with a cover flange that prevents the surgeon'hand from contacting any non-sterile portions of the handle while he is manipulating it. However, the cover having this flange is not as effective as the drape which enables the surgeon to manipulate the handle without looking away from the eye-pieces and the efficiency of the surgical operation will unavoidably decrease since the surgeon has to look away from the eyepieces each time he or she wants to make sure that there is no contact with the non-sterile portions of the equipment.